The present invention relates to the art of airbrushes, and in particular to an improvement in the means for selecting any one of a group of colors stored in an array of small bottles or for blending adjacent colors of a spectrum represented by the group of stored colors.
Prior art airbrushes in general, and in particular airbrush assemblies having the capability of switching from one color to another selected from a group of preselected colors as disclosed by Ronald A. Gress in U.S. Pat. No. 4,508,271 (which by this reference is hereby incorporated herein) are shaped to be held like a pencil with a nozzle at a tip end. A source of pressurized air is connected to the airbrush at a point well behind the nozzle and behind a short section that includes a venturi. As the velocity of the pressurized air increases in passing through a constrictive throat in the venturi, air pressure decreases. Each of the array of small bottles storing different colors of paint has a flexible tube, one end of which is inserted through its bottle cap into the paint. The other end of each tube is connected to a selection means for coupling a selected tube, or an adjacent pair of the tubes in the case of blending two colors, to the venturi where the pressure of air flowing at increased velocity is lower than the static pressure of air over the paint in the bottles. In that manner, paint from one tube or two adjacent tubes is drawn into the venturi by suction and there entrained in the flowing air to the nozzle of the airbrush.
The paint selection means comprises three basic parts: a first part having a plurality of bores connected to respective flexible tubes inserted into the array of small bottles; a second part having a single bore for coupling a selected bore of the first part to an airbrush connector; and a valve plate affixed to the second part for selecting the bore of the first part to the single bore of the second part by pivoting the first part a fraction of a full turn relative to the second part.
The plurality of passages through the first part are disposed at radial distances from a central bore through which a bolt passes to so secure the valve plate to the first part so as to allow the first part to be pivoted by the artist relative to the second part. The second part includes a single bore for the passage of selected paint to a coupling at the other end of the bore directly to the airbrush. The valve plate includes a bore that matches on one side the single bore of the second part, but has an oval opening on the other side facing the first part with a major axis long enough to reach two adjacent bores connected to paint supply tubes when the valve plate is pivoted to a position having the center of the oval opening at the center between two adjacent bores connected to paint tubes, whereby the oval opening overlaps the adjacent tubes in order to select for blending two adjacent colors. Otherwise the valve plate is pivoted to a position having the center of the oval opening at the center of the selected paint supply bore while the valve plate covers adjacent paint supply bores in order to airbrush with only one color.
A problem with the prior art has been that when the needle valve in the airbrush is opened by the artist to paint, significant hesitation is experienced before paint mixes with the air sprayed out of the nozzle because of delay in the venturi sucking up paint into the tube and out into the airstream. A further problem is leakage of paint between the valve plate and the first part due to the weight of the first part and the flexible tubes connected to it. If a nut on the bolt is not tight or it loosens, the valve plate may tilt relative to the first part and the precision fit between the valve plate and that first part will fail, thus leaking paint, particularly while the artist is reversing airbrushing direction. This results in an unacceptable risk of leakage after extended use of the airbrush until the nut is again tightened on the bolt.
An object of the present invention is to provide a pressurized system for supplying paint to the airbrush venturi without delay each time the needle valve is opened. A further object is to eliminate the leakage problem in the color selection means of an airbrush and to integrate the airbrush and color selection means with an array of paint supply bottles, each bottle with regulated air pressure over the paint in the bottles to maintain a positive pressure on paint in the tube to the venturi in the airbrush ready for painting immediately after the needle valve is opened.
These and other objects of the invention are achieved in an integrated color selecting system for airbrushes with an improved color selection means comprising a disc having a convex surface on one side and a substantially flat surface on the other side thereof, and with an integral projection from the flat surface and an axial bore through the disc and projection. The projection serves the function of providing a paint-channel connection to the airbrush. A slant bore from the convex surface of the disc intersects the axial bore through the disc. The opening of the slant bore on the convex surface of the disc is centered a radial distance from the axial bore and is enlarged by a cavity that extends the reach of the slant bore on both sides for blending paint from adjacent bores equally spaced part at the same radial distance through a cylindrical block having an axial bore for a bolt and having a concave surface that matches the convex surface of the disc. The axial bore through the disc is countersunk on the convex side thereof to a depth that just does reach the slant bore and threaded to receive a short bolt passing through the axial bore of the cylindrical block to tighten the convex surface of the disc against the concave surface of the cylindrical block without intersecting the slant bore. The end of the countersunk bore is cut to present a conical surface to the end of the bolt when it is threaded in so that upon tightening the bolt a maximum force of friction is produced between engaging threads, thereby locking the bolt in place so that it will not turn relative to the disc while the cylindrical block is free to turn on the bolt.
The disc fits into a sleeve of uniform internal diameter and length substantially equal to the length of the cylindrical block. The sleeve has at one end (out of which the connector projection extends) an integral ring with a knurled surface for manually gripping the sleeve in order to pivot the sleeve about the axis of the disc. The disc is inserted with its connector projection extending out of the knurled ring of the sleeve, while the cylindrical block essentially covered by the sleeve. The cylindrical block includes two spaced O-rings press fit into grooves in the sleeve behind the disc with its concave surface against the convex surface of the disc. The O-rings maintain the axial alignment of the cylindrical block and disc with the sleeve and allow the cylindrical block to be pivoted with the sleeve. It should be noted that the disc itself will not pivot with the sleeve because its connector projection is held firmly by the coupling of the paint selecting means to the airbrush. The cylindrical block, preferably made of Teflon, is bored through from a flat face at one end and through the concave face at the other end to provide a number of parallel channels close to the O-ring grooves and spaced equally apart and at the same radial distance from the axis of the cylindrical block as the radial distance of the opening of the slant bore. These parallel channels allow paint to pass from their respective bottles to the interface of the concave and convex surfaces of the cylindrical block and the disc. The position of the slant bore opening at the interface selects a single color in one channel or, through the enlarged cavity around tat slant bore opening, a pair of adjacent colors for blending.
The parallel bores of the cylindrical block are countersunk through the flat surface to receive flexible paint tubes from the array of paint bottles, thus placing the O-ring grooves closer to the flexible paint tubes, preferably also made of Teflon. The paint tubes in the countersunk bores are thus locked in place by the O-rings, once the cylindrical block is press fit in the sleeve, due to the compressed O-rings crimping the paint tubes through a thin wall of the cylindrical block between the O-ring grooves and the countersunk bores for the paint tube.
The pressurized air applied to the airbrush while in use is also applied through a pressure regulator to a manifold which distributes air under steady pressure into the paint supply bottles so that the stored paint is always at a static pressure for maintaining the flexible tubes loaded with paint to the color selection and blending means in order that, when a needle valve in the airbrush is opened, the paint will be at the airbrush ready for mixing without having to rely on a venturi in the airbrush to draw paint three the paint tubes. All of flexible paint tubes are bundled together by coiling the flexible pressurized air tube around them all the way from the pressure manifold to the airbrush. Each of the bottle caps are attached to the pressure manifold by a short, threaded bolt from the inside of the cap, and each flexible paint tube is passed from inside its paint bottle through the cap bolt into the pressure manifold. The hole in the caps is of a diameter relative to the diameter of the tubes to allow air to seep from the pressure manifold into the bottles, thus maintaining air pressure over paint in the bottles at the regulated pressure in the bottle.
At the end of the manifold opposite the pressure regulator, all flexible paint tubes are passed through pressure relief means comprising a plug inside valve inserted into the manifold. That pressure relief is set by a spring at a pressure limit above the normal range of up to 25 psi at which the pressure regulator set, which is still below the pressure that the paint bottles can withstand. The spring holds the plug valve against a valve seat and the tubes pass through the valve seat and the plug valve. Any excess pressure will force the plug valve to open against the spring.